In continuation of our work aimed at the design and evaluation of long-acting complexes of narcotic antagonist drugs for the treatment of addiction, our most promising preparations to date, naltrexone zinc tannate and naltrexone aluminum tannate will be studied in greater depth with respect to their chemical and pharmacological properties. Their duration of activity in animals will be further evaluated and correlated with maintenance of blood and/or urine levels. To the extent possible, the pharmacolinetics of these preparations, their metabolism, tissue distribution and excretion, will be studied in comparison with naltrexone hydrochloride. Complexes of other promising narcotic antagonist candidate drugs will be prepared as these drugs become available.